omfs: add bitmap routines

Add block allocation and block bitmap management routines for OMFS.

Signed-off-by: Bob Copeland <me@bobcopeland.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/omfs/bitmap.c b/fs/omfs/bitmap.c
new file mode 100644 (file)
index 0000000..dc75f22
--- /dev/null
+++ b/fs/omfs/bitmap.c
@@ -0,0 +1,192 @@
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/buffer_head.h>
+#include <asm/div64.h>
+#include "omfs.h"
+
+unsigned long omfs_count_free(struct super_block *sb)
+{
+       unsigned int i;
+       unsigned long sum = 0;
+       struct omfs_sb_info *sbi = OMFS_SB(sb);
+       int nbits = sb->s_blocksize * 8;
+
+       for (i = 0; i < sbi->s_imap_size; i++)
+               sum += nbits - bitmap_weight(sbi->s_imap[i], nbits);
+
+       return sum;
+}
+
+/*
+ *  Counts the run of zero bits starting at bit up to max.
+ *  It handles the case where a run might spill over a buffer.
+ *  Called with bitmap lock.
+ */
+static int count_run(unsigned long **addr, int nbits,
+               int addrlen, int bit, int max)
+{
+       int count = 0;
+       int x;
+
+       for (; addrlen > 0; addrlen--, addr++) {
+               x = find_next_bit(*addr, nbits, bit);
+               count += x - bit;
+
+               if (x < nbits || count > max)
+                       return min(count, max);
+
+               bit = 0;
+       }
+       return min(count, max);
+}
+
+/*
+ * Sets or clears the run of count bits starting with bit.
+ * Called with bitmap lock.
+ */
+static int set_run(struct super_block *sb, int map,
+               int nbits, int bit, int count, int set)
+{
+       int i;
+       int err;
+       struct buffer_head *bh;
+       struct omfs_sb_info *sbi = OMFS_SB(sb);
+
+       err = -ENOMEM;
+       bh = sb_bread(sb, clus_to_blk(sbi, sbi->s_bitmap_ino) + map);
+       if (!bh)
+               goto out;
+
+       for (i = 0; i < count; i++, bit++) {
+               if (bit >= nbits) {
+                       bit = 0;
+                       map++;
+
+                       mark_buffer_dirty(bh);
+                       brelse(bh);
+                       bh = sb_bread(sb,
+                               clus_to_blk(sbi, sbi->s_bitmap_ino) + map);
+                       if (!bh)
+                               goto out;
+               }
+               if (set) {
+                       set_bit(bit, sbi->s_imap[map]);
+                       set_bit(bit, (long *) bh->b_data);
+               } else {
+                       clear_bit(bit, sbi->s_imap[map]);
+                       clear_bit(bit, (long *) bh->b_data);
+               }
+       }
+       mark_buffer_dirty(bh);
+       brelse(bh);
+       err = 0;
+out:
+       return err;
+}
+
+/*
+ * Tries to allocate exactly one block.  Returns true if sucessful.
+ */
+int omfs_allocate_block(struct super_block *sb, u64 block)
+{
+       struct buffer_head *bh;
+       struct omfs_sb_info *sbi = OMFS_SB(sb);
+       int bits_per_entry = 8 * sb->s_blocksize;
+       int map, bit;
+       int ret = 0;
+       u64 tmp;
+
+       tmp = block;
+       bit = do_div(tmp, bits_per_entry);
+       map = tmp;
+
+       mutex_lock(&sbi->s_bitmap_lock);
+       if (map >= sbi->s_imap_size || test_and_set_bit(bit, sbi->s_imap[map]))
+               goto out;
+
+       if (sbi->s_bitmap_ino > 0) {
+               bh = sb_bread(sb, clus_to_blk(sbi, sbi->s_bitmap_ino) + map);
+               if (!bh)
+                       goto out;
+
+               set_bit(bit, (long *) bh->b_data);
+               mark_buffer_dirty(bh);
+               brelse(bh);
+       }
+       ret = 1;
+out:
+       mutex_unlock(&sbi->s_bitmap_lock);
+       return ret;
+}
+
+
+/*
+ *  Tries to allocate a set of blocks. The request size depends on the
+ *  type: for inodes, we must allocate sbi->s_mirrors blocks, and for file
+ *  blocks, we try to allocate sbi->s_clustersize, but can always get away
+ *  with just one block.
+ */
+int omfs_allocate_range(struct super_block *sb,
+                       int min_request,
+                       int max_request,
+                       u64 *return_block,
+                       int *return_size)
+{
+       struct omfs_sb_info *sbi = OMFS_SB(sb);
+       int bits_per_entry = 8 * sb->s_blocksize;
+       int ret = 0;
+       int i, run, bit;
+
+       mutex_lock(&sbi->s_bitmap_lock);
+       for (i = 0; i < sbi->s_imap_size; i++) {
+               bit = 0;
+               while (bit < bits_per_entry) {
+                       bit = find_next_zero_bit(sbi->s_imap[i], bits_per_entry,
+                               bit);
+
+                       if (bit == bits_per_entry)
+                               break;
+
+                       run = count_run(&sbi->s_imap[i], bits_per_entry,
+                               sbi->s_imap_size-i, bit, max_request);
+
+                       if (run >= min_request)
+                               goto found;
+                       bit += run;
+               }
+       }
+       ret = -ENOSPC;
+       goto out;
+
+found:
+       *return_block = i * bits_per_entry + bit;
+       *return_size = run;
+       ret = set_run(sb, i, bits_per_entry, bit, run, 1);
+
+out:
+       mutex_unlock(&sbi->s_bitmap_lock);
+       return ret;
+}
+
+/*
+ * Clears count bits starting at a given block.
+ */
+int omfs_clear_range(struct super_block *sb, u64 block, int count)
+{
+       struct omfs_sb_info *sbi = OMFS_SB(sb);
+       int bits_per_entry = 8 * sb->s_blocksize;
+       u64 tmp;
+       int map, bit, ret;
+
+       tmp = block;
+       bit = do_div(tmp, bits_per_entry);
+       map = tmp;
+
+       if (map >= sbi->s_imap_size)
+               return 0;
+
+       mutex_lock(&sbi->s_bitmap_lock);
+       ret = set_run(sb, map, bits_per_entry, bit, count, 0);
+       mutex_unlock(&sbi->s_bitmap_lock);
+       return ret;
+}